We evaluate whether high spectral and spatial resolution (HiSS) BOLD MRI can correctly rank the effects of three tumor-oxygenating treatments on radiosensitivity in BA1112 rhabdomyosarcomas (n = 5). Significant decreases in spectral linewidth predict that treatment with carbogen gas combined with a perfluorocarbon emulsion will increase radiosensitivity more than either treatment alone, which agrees with the known effects of these treatments on hypoxic fraction. High-resolution maps show that tumor response to each treatment is spatially heterogeneous, and that there is a paradoxical response to the treatments in 7-12% of tumor pixels. Because HiSS MRI emphasizes changes in necrotic and/or hemorrhagic regions, it is more sensitive to oxygenation changes compared to conventional MRI. These results demonstrate that HiSS MRI is a practical, noninvasive method that could be used to choose the treatment that maximizes the size and extent of increases in tumor oxygenation for individual patients.